When you arrive in Birštonas resort, you will notice the road signs of Sonata hotel and using it you will easily find the hotel.
If you some how did not notice any signs, than you should go the main street and after the last lake you will need to turn left to the first street (Pušyno str.). Then you go almost to the end of this street and turn to the last street on you right. After 150m you will see the Sonata hotel at your left.